It is clear to all now that Russian President Vladimir Putin is a world class liar. He can’t be trusted. He’s a leader who is a threat not only to the Ukraine but to other countries.

He wants to bring Russia back to what it was when it was the Soviet Union. That won’t happen but he can make some conquests, and he’s beginning with trying to convince the world he simply is protecting Russia’s interests and the Russian-speaking people who live in a section of the Ukraine.

There is no doubt that his actions in Crimea over the weekend were planned well in advance. He would like all of the Ukraine but for now will settle for part of that country. The Ukraine once was part of the Soviet Union. The country has had its problems as a democracy and conditions are very unsettled now. The corrupt president, Viktor Yanukovych, rejected a partnership with the European Union in favor of a partnership with Russia. The antigovernment insurgents forced him to leave Kiev, capital of the Ukraine, and he now is in Russia.

The United States and several European countries have warned Putin that his actions are posing serious consequences, but he has dismissed all of those threats. Military action has not been threatened, but economic sanctions may be imposed, and should be. The United States and other European nations need to take serious actions and show Putin that they mean business. Unfortunately, when President Obama drew that “red line” in the Syrian conflict, and then backed down, it was a sign of weakness to the world. Putin views Obama as a weak leader.

In the background of all of this, and Putin knows this, is that the U.S. needs cooperation from Russia on several fronts, as pointed out by the Associated Press. Russian cooperation is needed in putting an end to the civil war in Syria; negotiating a nuclear accord with Iran; and transporting American troops and equipment out of Afghanistan through Russian supply routes.

However, Putin must be given a lesson from the U.S. and European countries that his aggression will not be tolerated. It appears that the only option is economic sanctions.